1. Field of the Invention
This invention relates to processes for making multifunction integrated optics chips having optimally high electro-optic coefficients, and proton-exchanged, preferably rhombohedral structure, and to the multifunction integrated optics chips resulting from these processes.
2. Description of Related Art
Until now, the methods for making multifunction integrated optics chips, particularly such chips made of lithium niobate, have included the step of subjecting the chips to proton exchange with acids such as benzoic acid at temperatures in the range of about 150.degree. C. to about 250.degree. C. for times of about 10 to about 20 minutes or more. Where the proton exchange step is carried out at higher temperatures or for longer times, or both, the lithium niobate substrates tend to form substantial internal stresses that result in microcracking in the substrate areas exposed to the proton exchange step. As a result, the chips made by processes including this step frequently exhibit refractive index instabilities, high propagation losses, and low electro-optic coefficients.